Question

For first order reaction it take 5 minutes to initial conc. Of 0.6 m to become 0.4 m how long will it take to become 0.3 m.

Answer 1

Answer: 8.35 minutes

Explanation:

Rate law follows first order kinetics.

$N=N_o\times e^{-\lambda t}$

N = amount left after time t  = 0.4 M

$N_0$ = initial amount  = 0.6 M

$\lambda$ = rate constant

t= time  = 5minutes

$0.4=0.6\times e^{-\lambda\times 5minutes}$

$\lambda=0.083minutes^{-1}$

Now, N = amount left after time t  = 0.3 M, we need to find t

Again putting in the values:

$0.3=0.6\times e^{-0.083minutes^{-1}\times tminutes}$

$t=8.35minutes$

It will take 8.35 minutes to reduce 0.6 m to 0.3 m.